OK, how could this result come about for both Himalayan kingdoms, displacing Buddhism & Hinduism respectively ?
Might you be thinking of The Crusading Khan? It was posted on SHWI. IIRC it ends with a Mongol being crowned by the pope as Holy Emperor of the Orient, so you know it's gonna be a hell of a story.I'm no expert on Asia(hell, I know barely anything about it in this time period) but I do remember one TL, whose name escapes me, where Xadu Khan a Nestorian Christian takes the place of Ghengis Khan and still achieves many of his conquests. Explicitly Nestorian Mongols(as opposed to the religious freedom ones of OTL) could possibly have a good chance at prosletyzing in many areas of their empire. I don't think that would completely displace hinduism and buddhism but it might make a serious competitor.
Like I said though, I know very little about this area, so that might not actually work.